Characterization of a new tymovirus causing stunting and chlorotic mosaic in naranjilla (Solanum quitoense)

Authors: GREEN, KELSIE - University Of Idaho; Mollov, Dimitre; TRAN, LISA - University Of Idaho; ALVAREZ-QUINTO, ROBERT - Centro De Investigaciones Biotecnologicas Del Ecuador; OCHOA, JOSE - National Institute For Agricultural Research (INIAP); QUITO-AVILA, DIEGO - Centro De Investigaciones Biotecnologicas Del Ecuador; KARASEV, ALEXANDER - University Of Idaho

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2017
Publication Date: 3/10/2018
Citation: Green, K., Mollov, D.S., Tran, L., Alvarez-Quinto, R., Ochoa, J., Quito-Avila, D., Karasev, A. 2018. Characterization of a new tymovirus causing stunting and chlorotic mosaic in naranjilla (Solanum quitoense). Plant Disease. 102:911-918.

Interpretive Summary: Naranjilla is a perennial shrub cultivated in the Andes for fresh fruit and juice production. Naranjilla plants in Ecuador were observed with virus-like symptoms. High throughput sequencing analysis revealed a new virus that might be associated with the symptoms. Transmission electron microscopy observations confirmed spherical virus particles. Four indicator plants (naranjilla, tamarillo, N. benthamiana, and eggplant) were mechanically inoculated with sap from the symptomatic naranjilla. The inoculated plants developed symptoms and virus infections were confirmed. The complete genomic sequence of this virus, named naranjilla chlorotic mosaic virus (NarCMV) was determined. Virions were used to produce antibodies. Based on genome sequence comparisons to known viruses, NarCMV was characterized as new virus of the genus Tymovirus, in the family Tymoviridae. The NarCMV genome sequence and the available antibodies facilitate developing detection methods, and subsequently control measures, for this newly described virus. This information will be useful to growers and regulatory agencies.

Technical Abstract: Naranjilla (“little orange”), also known as lulo (Solanum quitoense Lam.), is a perennial shrub species cultivated in the Andes for fresh fruit and juice production. In 2015, a naranjilla plant exhibiting stunting, mosaic, and chlorotic spots was sampled in the Pastaza province of Ecuador and maintained under greenhouse conditions. An infectious agent was mechanically transmitted to indicator plants and was subjected to biological and molecular characterization. Spherical particles ca. 30 nm in diameter, composed of a single 20-kDa capsid protein, were observed under electron microscope in infected naranjilla plants. High throughput sequencing conducted on inoculated Nicotiana benthamiana plants produced a single sequence contig sharing the closest relationship with several tymoviruses. The entire 6,283-nt genome of a new tymovirus was amplified using RT-PCR and re-sequenced with the Sanger methodology. The genome had three open reading frames typical of tymoviruses, and displayed a whole genome nucleotide identity level with the closest tymovirus, Eggplant mosaic virus, at 71% (90% coverage). This tymovirus from naranjilla was able to systemically infect eggplant, tamarillo, N. benthamiana, and naranjilla. In naranjilla, it produced mosaic, chlorotic spots, and stunting, similar to the symptoms observed in the original plant. The virus was unable to infect potato and tobacco, and unable to systemically infect pepper plants, replicating only in inoculated leaves. We concluded that this virus represented a new tymovirus infecting naranjilla, and proposed the tentative name naranjilla chlorotic mosaic virus (NarCMV).